Building construction

ABSTRACT

As standard practice, a window construction has a window surround and a window frame secured and sealed thereto. According to the invention, the window frame and window surround have facing sealing surfaces with a resilient seal therebetween and also facing jamming surfaces with a strip-like jamming member inserted therebetween to compress the seal to a desired extent and secure the window frame in position.

United States Patent [191 Alabaster I 1 BUILDING CONSTRUCTION [75] Inventor: Leonard Frederick Peter Alabaster, Alresford, Nr Winchester, England [73] Assignee: Conder International Limited,

Winchesten England [22} Filed: Jan. 15, 1974 [21] Appl. No: 433.529

[30] Foreign Application Priority Data Jan IS 1973 United Kingdom 2126/73 Mar. 6, 1973 United Kingdom 10836/73 [52] US. Cl. 52/97; 52/204; 52/209 [51] Int. CI. E06B 7/14; E06B 3/62 [58] Field of Search 52/97 204-214, 52/400, 402, 403. 624 309; 49/DIG. 1 504 [56] References Cited UNITED STATES PATENTS 3004.305 10/1961 Goodemote et a1. 1. 52/402 X 3.331184 7/1967 McEvoy 52/204 III-T NOV. 18, 1975 3.362.123 1/1968 Geyser 52/209 X 3.418.773 12/1968 Sarvay 52/400 3.571.994 3/1971 Brown 52/309 FOREIGN PATENTS OR APPLICATIONS 628292 8/1949 UlliICd Kingdom r r r a 52/214 522.545 3/1956 Canada a a a a a r r r 4 a 51/304 Primary E.\'uminer-.l. Karl Bell Attorney, Agent, or FirmParme1ee. Miller Welsh & Kratz 1 1 ABSTRACT As standard practice, a window construction has a window surround and a window frame secured and sealed thereto. According to the invention. the window frame and window surround have facing sealing surfaces with a resilient seal therebetween and also facing jamming surfaces with a strip-like jamming member inserted therebetween to compress the seal to a desired extent and secure the window frame in position.

8 Claims, 10 Drawing Figures US. Patent Nov. 18 1975 Sheet20f5 3,919,815

US. Patent Nov. 18, 1975 Sheet30f5 3,919,815

F IGA.

US. Patent Nov. 18, 1975 Sheet 4 0f 5 3,919,815

BUILDING CJONSTRUCTION BACKGROUND OF THE INVENTION This invention relates to a window construction having a window surround and a window frame secured therein and sealed thereto.

It is an object of the invention to provide a screwless but watertight assembly which enables the window frame to be fitted into position on,site whilst allowing normal manufacturing tolerances in the components, and also to provide an assembly in which resilient seals are used but are neither over-compressed nor undercompressed.

BRIEF DESCRIPTION OF THE lNVENTlON According to the invention, at least one of the sides, sill and head of the window surround has a generally rearwards-facing sealing surface, a generally forwardsfacing jamming surface being spaced to the rear of the sealing surface, and the corresponding side, bottom or top of the window frame correspondingly having a generally forwards-facing sealing surface cooperating with the sealing surface of the window surround with a resilient seal between the two sealing surfaces, and a generally rearwards-facing jamming surface spaced to the rear of the sealing surface of the frame, spaced in front of the jamming surface of the window surround, a striplike jamming member being inserted between the two jamming surfaces and thrusting the sealing surface of the frame forwards against the sealing surface of the window surround. t

The jamming arrangement provides a screwless but watertight assembly which nonetheless permits relatively large tolerancesand speedy fitting of the window frame on site. The window construction can provide efiicient weather-tight glazing in preformed window apertures in a wall construction which is subject to normal constructional tolerances.

If as is preferred, a jamming member is used which is designed to be driven right home to provide a predetermined spacing between the two respective jamming surfaces, the construction can be designed tolapply a controlled compression to the resilient seal.

The jamming arrangement ispreferablyapplied to just the sill and the head, but may also oralternatively be applied to one or both of the sides, provided the frame can be placed in position without undue difficulty.

The jamming surfaces need not be even approximately vertical, and the jamming surface on the window surround is preferably inclined at an angle of approximately 45 to give a wedge action when the jamming member is inserted.

The jamming member can be made of a plastics material such as polyvinyl chloride. The jamming member is preferably a long strip for extending along the whole of the edge of the respective frame, giving a neat finish. if, as is preferred, the strip is flexible, it can be fed into position without difficulty, e.g. from a coil.

The jamming member preferably has a rebate, along its top front edge, for forming a condensation drainage channel; there may be vertical channels along the front surface of the wedge for draining condensation down out of the channel or holes drilled down through the strip, or the strip ends may be mitred for this purpose.

A building construction normally has vertical gaps between adjacent building members such as window frames, and the gaps are sealed by suitable intermediate members. lt is an object of the invention to provide a sealing arrangement which is simple to fit on site, neither over-compressed nor under-compressed resilient seales used, permits normal manufacturing tolerances and can have agood appearance. According to an important aspect of the invention, the intermediate member is a coupling member of, or having a part of, T shape as seen in horizontal section, the stem of the T projecting into the gap (preferably from the outside) so as to extend through to the other side of the building members, and the two end portions of the cross-bar of the T overlapping the edge portions of the respective building members, resilient seals being positioned between the respective end portions of the T cross-bar and said edge portions of the building members and being compressed by drawing on the stem of the T, the coupling member being retained by retaining devices in a position compressing the seals, which retaining devices cooperate with the building members.

The stem of the T can be drawn by means of a tool and the coupling member can give a good seal while avoiding the use of screws and nonetheless permitting variations in the width of the vertical gap, due to manufacturing tolerances. in addition, there can be controlled compression of the seals in that by suitable dimensioning, the seal will be neither too much compressed nor too little compressed.

The cross-bar portion of the coupling member can be designed to have a good appearance, particularly where it is acting as a mullion between two window frames, and the retaining means can be arranged to be concealed by a cap, to improve the appearance.

The retaining devices preferably comprise a number of vertically-spaced, horizontal cross-members engaging the surfaces of the building members on the other side thereof to said edge portions, each cross-member bridging said gap and engaging the end portion of the stem of the T, preferably by passing through a crossaperture in the stem end portion. The cross members preferably have locating detents on their ends for engagement by small projections on the inside of a snapon vertical channel-section cap, for concealing the retaining devices.

The cross-bar of the T can have locating detents, e.g. on its ends for engagement by small projections on the inside of a snap-on vertical channel-section cap for covering the cross-bar and giving a bolder appearance to this side of the coupling member, particularly where the coupling member is sealing the vertical gap be tween window frames and the cap acts as a mullion. The mullion cap so formed can give stronger architectural effect to the windows.

In a building construction there are often joints formed between aligned thin section building members, such as extruded aluminum sill sections, whose edges are separated by a narrow gap sealed by the interposition of a seal. It is an object of the invention to provide a method of forming the seal which formed an effective seal with components of normal manufacturing tolerances and a seal which has a good appearance if it is to be visible, but which method however can be performed by unskilled labour.

According to an important aspect of the invention, the sea seal is inserted by placing an easily deformable sealing material, e.g. a substantially non-elastic but ex trudable material such as mastic, in a channel in a sub or backing member, which channel will be behind and run the length of the gap and will be substantially wider than the width of the gap, and the cross-sectional area of the sealing material being substantially greater than the cross-sectional area of the channel, and drawing the edge portions of the buildiing members against the sub or backing member to squeeze some of the sealing material up into the gap between the edges of the building members.

This construction gives a good seal in a gap which is difficult to seal. and the sealing material need not spread sideways beyond the channel to a substantial extent beneath or behind the building members and need not project beyond the exposed faces of the building members because a controlled thickness of sealing material can be provided in a controlled channel depth. particularly when using a strip of sealing material; nonetheless. the sealing material is firmly fixed in position. The construction can however accommodate variations in the width of the gap due to manufacturing tolerances.

The seal is particularly useful for sealing the external parts of window sills. or external window sills, together; the sub or backing member can be a pre-formed member which is placed on the building wall before placing the sills in position, and the sill end portions can be drawn against the sub or backing member by fixing the sills for instance to the wall.

The invention will be further described, by way of example. with reference to the accompanying drawings. in which:

FIG I is a vertical section through the lower part of a window construction in accordance with the invention, along the line ll of FIG. 4;

FIG. 2 is a vertical section, on a larger scale, through the jamming member shown in FIG. I, with a small modification;

FIG. 3 is an isometric, exploded view, showing the lower part of the window construction at the joint between two sills;

FIG. 4 is a horizontal section along the line IVIV of FIG. 1, showing the centre mullion and the sealing between two windows;

FIG. 5 is an isometric view of a special tool for drawing back the coupling member;

FIG. 6 is a vertical section along the line VIVI of FIG. 4; and

FIG. 7 is a vertical section, taken higher up the building than the section of FIG. I but generally corresponding thereto though showing a modified sill arrangement.

FIGS. 80 to Sc illustrate the manner in which the jamming member is inserted between the window surround jamming surface and the window frame jamming surface.

The building shown in the drawings has its main wall structure made of large concrete units 1, these units 1 being suitably supported; an outer cladding 2 may be provided. and the outer cladding 2 may have a suitable coping 3 below the level of the window sills. The building has a number of side-by-side double-glazed windows, each window being formed as a standard unit of any suitable number of panes 4 secured in e.g. an extruded aluminium frame 5 by means of e. g. snap-in sections 6. The frames 5 rest on a main sill 7 which is screwed to the top of the lower wall unit I, the main sill 7 having an external sill 8 and an internal sill 9. A head section [0 (FIG. 7) is mounted above the window frames 5 and is screwed to the bottom of an upper wall unit I.

POST APPLIED EXTERNAL SILL As shown in FIG I, the main sill 7 has an external overhang with a sloping top piece 2] and a rearwardlyprojecting lower piece or flange 22, a gap being left inwards of the inner edge of the lower piece 22. The external sill 8 has an upstand 23 which passes up through the gap and has a forwardly-projecting part in the form of a curled-over upper end 24 which rests on the overhang lower piece 22. The rear surface of the upstand 23 either lies flush against, or lies parallel to and close to, a vertical wall 25 on the main sill 7. The base of the rear portion 26 of the external sill 8 does not quite touch the adjacent surface 27 of the main sill 7.

In order to place the external sill 8 in position, the curled-over upper end 24 is passed up through the gap referred to above with the front of the external sill 8 raised, and the front of the external sill is then lowered into its proper position. The external sill 8 can then be secured in position. for instance by being bolted or riveted to splice plates 29 (as shown in FIG. I) or to brackets (not shown); the splice plates 29 are described in more detail below with reference to FIG. 3. The heads of the screws or rivets can be concealed by mullion capping 30, described in more detail below with reference to FIG. 4, provided the screws or rivets are only used at the join between adjacent window frames 5.

In the arrangement shown in FIG. I, the front edge of the external sill 8 just projects over the rear edge of the coping 3. However, a different arrangement is indicated in FIG. 7, where there is no coping on the outer cladding (not shown); the external sill 8a is wider and projects right out beyond the forward edge of the outer cladding.

BOTTOM LOCATION AND RETENTION OF wmoow FRAME The main sill 7 has a step in its front portion providing a vertical, rearward facing sealing surface 41 and a horizontal support surface 42., the support surface 42 terminating in an inclined guide lip 43. Prior to inserting the window frame 5, a sealing strip 44 having one adhesive surface is stuck to the sealing surface 4] by means of the adhesive surface.

The main sill 7 may also have a rearwardly-projecting retaining lip 45 spaced above a rear support lip 46 and facing a retaining flange 47 having a forwardly-projecting detent lip 48 along its top edge. The retaining lip 45 is however omitted in FIG. 7.

To insert the window frame 5, the frame 5 is tilted forwards somewhat and its top is inserted up into the head section 10 (see the dashed outline in FIG. 7); the frame bottom is then swung forwards and the frame 5 dropped down until the front support flange 50 engages the guide lip 43 and slides down onto the sill support surface 42. The top of the frame 5 is then fixed in position as described below. The bottom of the frame 5 can be pushed forward by hand so that the front of the support flange 50 is firmly against the sealing strip 44.

A jamming member in the form of a wedge strip 53 (see FIG. 2), made of hard but flexible and somewhat resilient material such as polyvinyl chloride, is now inserted from a roll into the gap between the rear surface (the jamming surface) of the frame flange 51 and the sill retaining flange 47. This is done by tilting the wedge strip 53 slightly backwards and then inserting its lower portion or leg 54 through the gap before the jamming action commences and before tilting the strip 53 into the correct position and tapping it home. As shown in FIGS. 8a to Sc wedge strip 53 can be tilted backwards through an angle of about 45 until the inclined front surface of the lower portion or leg 54 is parallel to the rear or jamming surface of the frame flange 51, thus permitting simple insertion of the relatively thin leg 54, even though the window frame 5 will be slightly to the rear of its final position, making the gap between the rear or jamming surface of the frame flange 51 and the detent lip 48 rather small. As the strip 53 is tapped right home, it initially has a wedging action as the inclined upper side of the horizontal channel in the rear of the strip 53 rides over the inclined generally forwards-facing jamming surface of the detent lip 48; then the detent lip 48 engages in successive detent grooves 55 on the rear of the strip 53 and prevents easy removal of the strip. The strip 53 thus has a wedging and jamming action and presses the support flange 50 firmly against the sealing strip 44, the strip both sealing and locating the bottom of the window frame.

DRAINAGE OF CONDENSATION FROM INSIDE OF WINDOW PANE As can be seen in FIGS. 1 and 2, the wedge strip 53 has a rebate 61 in its top front edge, forming a channel with the frame flange 51 for receiving condensation running off the window pane and over the sections 6 and back of the frame 5. If desired, a groove 62 can be formed along the front face of the wedge strip 53, as shown in FIG. 1 but not in FIG. 2, in order to maintain a nearly constant thickness of section for extrusion, though this is not considered essential. Vertical channels may be spaced along the front of the wedge strip 53 or spaced holes may be drilled down through the wedge strip 53 so that the condensation can drain down into a channel 63 formed in the main sill 7; however, it is preferred that each wedge strip only extends for the width of one window, and its ends are mitred for this purpose, as visible at 530 in FIG. 4. In front of the channel 63, there is a fixing channel 64 in the base of the main sill 7 and then a shallow drainage channel 65 lying above a rebate containing a bottom sealing strip 66. The condensation is taken over the fixing channel 64 by means of ducts in the form of U-section aluminium channels 67 which are for instance welded into position. From the channel 65, the condensation passes out through front openings 68 on to the top of the wall unit 1 and then pools and flows out beneath the front lip 69 of the main sill 7.

SPLICE PLATE COUPLING BETWEEN SILLS The main, external and internal, sills 7, 8, 9 are in sections, butt joints being made between the sections in the vertical plane of the joints between the window frames 5; there will also be a joint between adjacent wall units 1, lying in the same plane. Prior to placing the main sills 7 in position, a splice plate 29 (see FIG. 3) has its spine 72 inserted into the joint between the lower wall units 1 (this joint being a gap of for instance mm. width) and the splice plate 29 is screwed down. The splice plate 29 has a profiled front portion 73 which acts as a sub or backing member and is shaped so that its front and upper surfaces mate with respective surfaces on the underside of the external and main sills 6 8, 7 (see FIG. 1), the end of the support flange 51 being cut away (see FIG. 3).

As can be seen in FIG. 4. the front portion 73 has a wide, shallow channel or groove 74 which runs along the whole of its front, top and rear surfaces. Prior to placing the main and external sills 7, 8 in position, a mastic sealing strip 75 (see FIG. 6) of flat, rectangular section is placed in the groove 74, the top of the mastic strip 75 protruding out of the groove 74; thus the groove 74 can be 2 mm. deep while the mastic strip 75 is 3 mm. thick. When the main sills 7 and subsequently the external sills 8 are fixed in position, some of the mastic squezzes up into the gap or joint between the ends of the sills so that the strip assumes the inverted T shape shown in FIG. 6.

The internal sills 9 can be placed in position after fixing the main sills 7 and are located against longitudinal movement by a low, notched rib 76 running along the top of the splice plate 29 between wings 77 which are used to support the internal sills 9 and screw the splice plate 29 to the top of the wall units 1.

TOP RETENTION OF WINDOW FRAME The top of the window frame 5 is inserted up into the head section 10 (see FIG. 7) and its top front flangc 91 is adjacent a sealing strip 92 which is stuck to a depending flange 93 on the head section 10. The frame 5 is then dropped until it is supported by the main sill 7. A wedge strip 53 is then tapped home between a rear flange I01 of the head section I0 and the rear flange 102 of the frame 5 in exactly the same way as the bottom wedge strip 53 is inserted, compressing the scaling strip 92.

The building is constructed so that the tops of the units are accurately aligned, all tolerances being taken out of the bottoms of the units; thus the bottom of one unit 1 may be up to for instance 6 mm above or below the bottom of the adjacent unit 1. The joints between the head sections 10 are in the same vertical planes as the joints between the units 1 and thus adjacent head sections can be mis-aligned in a vertical direction.

COUPLING AND SEALING BETWEEN WINDOW FRAMES As can be seen in FIG. 4, there is a vertical gap between the front flanges of the window frames 5. When one window frame 5 has been fixed in position, a coupling member 132 has its stern 133 rested against one side of the fixed frame 5 with its rear end projecting out behind the rear surface 134 of the fixed frame 5, resilient sealing strips 135 having been stuck to the rear surfaces of the cross-bar" 136. The bottom of the coupling member 132 is located by being inserted in notches (not shown) cut in the retaining lip 45 and sloping top piece 21 of the sill. The top of the coupling member 132 is notched so that it projects up into the channel of the head section 10 or 100, locating it against forwards and backwards movement. The other window frame 5 is then inserted and fixed in position. The inside end of the stem 133 has a number of crossslots 137 spaced along its length and a spine 138 running the length of its rear edge. The spine 138 is gripped by a special tool (see the description of FIG. 5 below) which draws the stem 133 back and presses against the rear surfaces 134 of the frames, squeezing the sealing strips 135. When the stem 133 has been drawn back far enough, a horizontal cross-piece I39 is inserted in the respective cross-slot 137, the crosspiece 139 then bearing against the rear surfaces 134 on the frames 5. The cross-piece 139 is shown as having two small nibs 140 which engage on either side of the spine I38 and prevent accidental removal of the crosspiece I39. However, it is preferred to have only one such nib 140 and to insert adjacent cross-pieces 139 alternately from the left and from the right until the respective nib I40 abuts the side of the spine 138.

Each end of the cross-piece I39 has a locating detent; a channel-section cap 141 is now snapped on over the cross-pieces 139, the cap having nibs I42 which snap into the locating detents on the ends of the crosspieces I39. The cap 141 conceals the rear ends of the stems 133 and cross-pieces I39, and also prevents the cross-pieces 139 slipping sideways, should there be any tendency for this to occur.

On the outside, the coupling member 132 can be designed to be a mullion and give a good appearance to the window. However, the capping mullion 30 can be snapped on over the cross-bar 136, the cross-bar 136 having small detent grooves running down its edges and the capping mullion 30 having nibs 143 which snap into these grooves. The capping mullion 30 also has a small lip 144 within each side to prevent the mullion 30 being pushed on too far and has a further pair of nibs I45 which are referred to below.

The coupling member has projecting nibs 146 which prevent any water infiltration travelling to the inside of the building, and may have a front spine 147 to give it sufficient strength, the size of the front spine 147 being chosen to suit the wind loading expected.

SPECIAL TOOL FOR DRAWING BACK THE COUPLING MEMBER The tool is shown in FIG. 5, which is on a larger scale than FIG. 4.

The tool has jaws 171 which are passed over the rear spine 138 of the coupling member 132 until rubber wheels I72 bear on the rear surfaces 134 of the window frames 5. The wheels I72 are carried on a threaded spindle I73 which passes through longitudinal slots 174 in side plates 175 whose front ends form the jaws 171; nuts 176 on the spindle 173 are tightened to clamp and grip the spine 138 between the jaws 171. A lever 177 is pulled in a clockwise direction (as seen in FIG. and a cam 178, fixed to the lever 177 via a spindle 179, abuts the spindle 173 and forces it forwards, thus drawing back the spine 138 of the coupling member 132.

SEALING STRIPS The sealing strips 44, 92 and 135 may be made of Neoprene or polyethylene foam.

I claim:

1. A window construction for a building, comprising:

a window surround having two sides, a sill and a head, at least one of said sides, sill and head having a generally rearward-facing sealing surface and a generally forward-facing jamming surface spaced to the rear of said sealing surface;

a window frame in said window surround, said window frame having two sides, a bottom and a top and at least one of said sides, bottom and top having a generally forward-facing sealing surface adjacent and to the rear of said window surround seala resilient seal between said window surround sealing surface and said window frame sealing surface; and

a strip-like jamming member inserted between said window surround jamming surface and said window frame jamming surface and thrusting said window frame sealing surface against said window surround sealing surface by way of said resilient seal, said jamming member, as seen in vertical cross-section in position at the bottom of and securing said frame, having a front surface for engagement with said window frame jamming surface, an upper rear portion and a lower rear portion, said upper and lower rear portions having upper and lower rear surfaces for engagement with said window surround jamming surface, the upper and lower rear portions defining a recess therebetween, said recess having a generally concave surface the depth of said recess being such as to define a substantial space between the window surround jamming surface and said concave surface to facilitate insertion of the lower rear portion of the jamming member between the window frame jamming surface and the window surround jamming surface.

2. The window construction of claim I, wherein said 35 jamming surfaces are on said window surround sill and ing surface and a generally rearward-facing jamming surface spaced to the rear of said window frame sealing surface and adjacent and in front of said window surround jamming surface;

on said window frame bottom, and wherein said jamming member has a rebate along its top front edge, forming a condensation drainage channel, said window construction further comprising drainage duct means extending from said rebate to the outside of said buildmg.

3. A window construction for a building, comprising:

a window surround having two sides, a main sill, and

external sill and a head, said main sill defining an external overhang which comprises a top portion and a rearwardly-projecting lower portion spaced below said top portion, a gap being defined inwards of the inner edge of said lower portion, and said external sill having an upstand which passes up through said gap and defines a forwardly-projecting portion which is at least adjacent to said rearwardly-projecting lower portion of said main sill overhang, whereby said forwardly-projecting portion of said external sill upstand can be passed up through said gap with the front of said external sill raised and said external sill front then lowered into position to provide said external sill;

a window frame in said window surround, said window frame having two sides, a bottom and a top; sealing means sealing said window frame in said window surround; and

securing means securing said window frame in said window surround.

4. The window construction of claim 3, wherein said upstand of said external sill is substantially vertical and defines a forwardly-curledbver upper end forming said projecting portion, and wherein said main sill has a portion against whose front surface the rear surface of said upstand abuts.

5. A window construction comprising:

at least two window frames, said window frames being substantially co-planar and defining a vertical gap therebetween;

a coupling member having at least a part of T shape in horizontal section, said T comprising a stem and a cross-bar, said stem projecting into said gap and extending through to the inside of said window frame, and said cross-bar overlapping outside edge 9 portions of said window frames adjacent said gaps; resilient seals between respective end portions ofsaid cross-bar and said window frame outside edge por tions; and

retaining means inserted after placing said coupling member in position and retaining said coupling member in a position compressing said resilient seals. said retaining means cooperating with the in side edge portions of said window frames adjacent said gap, said retaining means comprising a plural ity of vertically spaced, horizontal cross members engaging said inside edge portions of said window frames, each said cross member bridging said gap and engaging in an aperture in the end portion of said stem of said T.

6. The window construction of claim 5, wherein a snap-on vertical channel-section cap is engaged over and conceals said cross-members, said cross-members defining locating detents on their ends, and said channel-section cap defining small projections on the inside thereof, said small projections engaging said detents.

7. The window construction of claim 5, wherein a snap-on vertical channel-section cap engages over and 10 covers said cross-bar of said 11 said cross-bar of said T defining locating detents and said channel-section cap defining small projections on the inside thereof, said small projections engaging said dctents.

8. A window construction comprising:

two aligned thin gauge sill sections defining a narrow gap thcrebetween;

a backing member beneath end portions of said sill sections and beneath said gap said backing member defining a channel which is substantially wider than the width of said gap and extends beneath said securing means drawing said end portions against said backing member; and

an easily deformable scaling material in said channel and extruded up into said gap, said sealing material having a cross-sectional area which is substantially greater than the crosssectional area of said channel, whereby part 0t said sealing material was squeezed up into said gap upon drawing said end portions against said backing member. 

1. A window construction for a building, comprising: a window surround having two sIdes, a sill and a head, at least one of said sides, sill and head having a generally rearwardfacing sealing surface and a generally forward-facing jamming surface spaced to the rear of said sealing surface; a window frame in said window surround, said window frame having two sides, a bottom and a top and at least one of said sides, bottom and top having a generally forward-facing sealing surface adjacent and to the rear of said window surround sealing surface and a generally rearward-facing jamming surface spaced to the rear of said window frame sealing surface and adjacent and in front of said window surround jamming surface; a resilient seal between said window surround sealing surface and said window frame sealing surface; and a strip-like jamming member inserted between said window surround jamming surface and said window frame jamming surface and thrusting said window frame sealing surface against said window surround sealing surface by way of said resilient seal, said jamming member, as seen in vertical cross-section in position at the bottom of and securing said frame, having a front surface for engagement with said window frame jamming surface, an upper rear portion and a lower rear portion, said upper and lower rear portions having upper and lower rear surfaces for engagement with said window surround jamming surface, the upper and lower rear portions defining a recess therebetween, said recess having a generally concave surface the depth of said recess being such as to define a substantial space between the window surround jamming surface and said concave surface to facilitate insertion of the lower rear portion of the jamming member between the window frame jamming surface and the window surround jamming surface.
 2. The window construction of claim 1, wherein said jamming surfaces are on said window surround sill and on said window frame bottom, and wherein said jamming member has a rebate along its top front edge, forming a condensation drainage channel, said window construction further comprising drainage duct means extending from said rebate to the outside of said building.
 3. A window construction for a building, comprising: a window surround having two sides, a main sill, and external sill and a head, said main sill defining an external overhang which comprises a top portion and a rearwardly-projecting lower portion spaced below said top portion, a gap being defined inwards of the inner edge of said lower portion, and said external sill having an upstand which passes up through said gap and defines a forwardly-projecting portion which is at least adjacent to said rearwardly-projecting lower portion of said main sill overhang, whereby said forwardly-projecting portion of said external sill upstand can be passed up through said gap with the front of said external sill raised and said external sill front then lowered into position to provide said external sill; a window frame in said window surround, said window frame having two sides, a bottom and a top; sealing means sealing said window frame in said window surround; and securing means securing said window frame in said window surround.
 4. The window construction of claim 3, wherein said upstand of said external sill is substantially vertical and defines a forwardly-curled-over upper end forming said projecting portion, and wherein said main sill has a portion against whose front surface the rear surface of said upstand abuts.
 5. A window construction comprising: at least two window frames, said window frames being substantially co-planar and defining a vertical gap therebetween; a coupling member having at least a part of T shape in horizontal section, said T comprising a stem and a cross-bar, said stem projecting into said gap and extending through to the inside of said window frame, and said cross-bar overlapping outside edge portions of said window frames adjacent said gaps; resilient seals between respective end portions of said crOss-bar and said window frame outside edge portions; and retaining means inserted after placing said coupling member in position and retaining said coupling member in a position compressing said resilient seals, said retaining means cooperating with the inside edge portions of said window frames adjacent said gap, said retaining means comprising a plurality of vertically spaced, horizontal cross members engaging said inside edge portions of said window frames, each said cross member bridging said gap and engaging in an aperture in the end portion of said stem of said T.
 6. The window construction of claim 5, wherein a snap-on vertical channel-section cap is engaged over and conceals said cross-members, said cross-members defining locating detents on their ends, and said channel-section cap defining small projections on the inside thereof, said small projections engaging said detents.
 7. The window construction of claim 5, wherein a snap-on vertical channel-section cap engages over and covers said cross-bar of said T, said cross-bar of said T defining locating detents and said channel-section cap defining small projections on the inside thereof, said small projections engaging said detents.
 8. A window construction comprising: two aligned, thin gauge sill sections defining a narrow gap therebetween; a backing member beneath end portions of said sill sections and beneath said gap, said backing member defining a channel which is substantially wider than the width of said gap and extends beneath said gap; securing means drawing said end portions against said backing member; and an easily deformable sealing material in said channel and extruded up into said gap, said sealing material having a cross-sectional area which is substantially greater than the cross-sectional area of said channel, whereby part of said sealing material was squeezed up into said gap upon drawing said end portions against said backing member. 